Output driver circuits, or simply “drivers,” transmit electronic signals onto various forms of communication channels, including transmission lines, cables, printed circuit board traces, or the like. There are many types and classes of drivers, each offering a combination of traits that make it more or less suitable for particular applications. For example, “single-ended” drivers transmit signals as a varying voltage or current signal over a single conductor. The main alternative to the single-ended approach is differential signaling, in which differential drivers transmit information as complementary signals over a pair of conductors. Single-ended drivers are simpler and less expensive, whereas differential drivers offer relatively higher noise tolerance.
Output drivers and the signaling schemes they support are not limited to differential or single-ended signaling. There are other classes of signaling, and many species of the various classes. Integrated-circuit (IC) vendors can design their ICs to include driver circuits optimized for a specific application, but often prefer to address a larger market by supporting multiple signaling schemes. The resulting drivers can be complex, area-intensive, and expensive, and one or more of the supported signaling schemes may suffer reduced performance as compared with a tailored solution. There is therefore a need for improved multi-modal drivers.